Inter facial architecture for nanostructured optoelectronic devices

ABSTRACT

An optoelectronic apparatus, a method for making the apparatus, and the use of the apparatus in an optoelectronic device are disclosed. The apparatus may include an active layer having a nanostructured network layer with a network of regularly spaced structures with spaces between neighboring structures. One or more network-filling materials are disposed in the spaces. At least one of the network-filling materials has complementary charge transfer properties with respect to the nanostructured network layer. An interfacial layer, configured to enhance an efficiency of the active layer, is disposed between the nanostructured network layer and the network-filling materials. The interfacial layer may be configured to provide (a) charge transfer between the two materials that exhibits different rates for forward versus backward transport; (b) differential light absorption to extend a range of wavelengths that the active layer can absorb; or (c) enhanced light absorption, which may be coupled with charge injection.

CROSS-REFERENCE TO AN EARLIER FILED APPLICATION

This application is related to U.S. patent application Ser. Nos.10/290,119, 10/303,665 and 10/319,406, the entire disclosures of whichare incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to optoelectronic devices and more particularlyto optoelectronic devices with nanostructured active layers.

BACKGROUND OF THE INVENTION

Optoelectronic devices interact with radiation and electric current.Such devices can be light-emitting devices that produce radiation as aresult of an applied electric voltage/current or photovoltaic (PV)devices, e.g., solar cells that produce an electric voltage/current as aresult of applied radiation. Optoelectronic devices typically one ormore active layers of photoactive material sandwiched between twoelectrodes. At least one of the electrodes is transparent. The activelayer typically includes two materials exhibiting complementary chargetransfer (e.g., one is an electron accepting/transporting material andthe other is a hole-accepting/transporting material). In the case of aPV device, at least one of the two materials is a light-absorbingmaterial. In an organic solar cell, radiation absorbed by the activelayer creates an exciton (an electron-hole pair) at an interface betweenthe two semiconductor materials. Holes and electrons diffuse through thetwo different materials such that electrons are collected at oneelectrode and holes are collected at the other. Unfortunately, electronsand holes can recombine before they are collected, which tends to limitthe efficiency of a PV device.

Recently, organic materials, such as gels, conjugated polymers,molecules, and oligomers, have been used as photoactive materials.Random blends of fullerenes and hole-accepting polymers have also beenused in organic PV cells. However, these random blends were lacking inorder. To increase the efficiency of optoelectronic devices it isdesirable to configure the active layer such that the presence of holeaccepting and electron accepting materials alternates on a scale oflength comparable to the exciton diffusion distance. This distance istypically on the order of several nanometers. To optimize efficiency ofthe active layer, it is desirable for the arrangement of thehole-accepting and electron-accepting materials to exhibit features ofregular shape, uniform size and uniform distribution. These featuresgive excitons a high probability of splitting into electrons and holes,which can migrate to each of their respective electrodes beforerecombining in the bulk material.

The performance of prior art PV cells is often sub-optimal for one ormore reasons. For example, it would be desirable to keep electrons onone side of the active layer and holes on the other, so they cannotrecombine before the electrons are pulled out of the device to generateelectricity. It would also be desirable for the active layer to absorblight over a broader range of wavelengths than is currently available ina single material. In addition, it would be desirable to enhance lightabsorption and/or charge injection from the light-absorbing material tothe electron-transporting material.

Thus, there is a need in the art for an active layer for anoptoelectronic device that overcomes the above disadvantages and acorresponding method of making such an active layer.

SUMMARY OF THE INVENTION

The disadvantages associated with the prior art are overcome byembodiments of the present invention directed to an optoelectronicapparatus, a method for making an active layer for an optoelectronicdevice, and the use of such an active layer in an optoelectronic device.

According to an embodiment of the present invention, an optoelectronicapparatus may include an active layer having a nanostructured networklayer having a network of regularly spaced structures with spacesbetween neighboring structures. One or more network-filling materialsare disposed in the spaces. At least one of the network-fillingmaterials has complementary charge transfer properties with respect tothe material of the nanostructured network layer. The interfacial layeris configured to enhance an efficiency of the device. The active layermay be disposed between two electrodes (at least one of which may betransparent) for use in an optoelectronic device.

In some embodiments, the interfacial layer can be configured such thatcharge-carriers traveling from the nanostructured network layer to thenetwork-filling material are transported at a different rate than thesame type of charge-carriers traveling from the network-filling materialto the nanostructured network layer. In other embodiments, theinterfacial layer can be configured to differentially absorb light,e.g., with two different phase-separated photoactive materials. Infurther embodiments, the interfacial layer may be configured to enhancelight absorption, charge injection or a combination of light absorptionand charge injection, e.g. with pigments or dyes.

Embodiments of the present invention provide more efficientoptoelectronic devices such as PV cells, in particular solar cells, atrelatively low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross-sectional schematic diagram of an active layerfor an optoelectronic device according to an embodiment of the presentinvention.

FIG. 2A depicts an isometric schematic diagram of carboxylic acidfunctionalized C₆₀.

FIG. 2B depicts an isometric schematic diagram of an alternativefunctionalized fullerene.

FIG. 3 depicts an isometric close-up view of a portion of a possiblestructure for a nanostructured network layer for use in an active layeraccording to an embodiment of the present invention.

FIG. 4 shows a cross-sectional schematic diagram of an optoelectronicdevice according to an embodiment of the present invention.

FIG. 5 is flow diagram illustrating a method of forming an active layerfor an optoelectronic device according to embodiments of the presentinvention.

DETAILED DESCRIPTION Contents

I. Glossary

II. General Overview

III. Optoelectronic Apparatus

IV. Optoelectronic Apparatus Fabrication

VI. Conclusion

I. GLOSSARY

The following terms are intended to have the following general meaningsas they are used herein:

Aspect Ratio: refers to the ratio of diameter to height or depth.

Buckminsterfullerene: is a molecule having a network of carbon atoms ina closed cage structure. Because of its soccer-ball-like shape, thebuckminsterfullerene molecule is often referred to as a “buckyball.”Molecules of this type are also known generally as fullerenes.

Complementary charge-transfer properties: As used herein, a first andsecond semiconductor or conductor materials are said to havecomplementary charge-transfer properties with respect to each other whenthe first material is a hole-acceptor and/or hole-transporter withrespect to the second and the second is an electron-acceptor and/orelectron-transporter with respect to the first or vice versa.

Device: An assembly or sub-assembly having one or more layers ofmaterial.

Efficiency: For an optoelectronic device or active layer, the efficiencyis the ratio of energy output (e.g., in the form of electrons) to thenecessary energy input (e.g., in the form of photons).

Fullerene: A molecule formed in a hollow, hexagonal or pentagonal groupshape. Fullerenes are a class of molecules that have many beneficialproperties. For example, some fullerenes, e.g. C₆₀ have a perfectlyspherical shape with a diameter of about 0.7 nm. Fullerenes also haveother useful forms, such as C₆₀, C₇₀, C₇₆, C₈₄, etc. Fullerenes havelarge, protected internal cavities which can be doped with othermolecules. Fullerenes have extremely high mechanical strength and veryhigh electronegativity. Fullerenes are soluble in organic solvents and,when functionalized, soluble in aqueous solutions, where they can bereactive. Each of these forms can be functionalized with one molecule,called a mono adduct, or with two molecules, called a dual adduct. Bothforms may be useful for applications in optoelectronic devices.

Hole-Acceptor, Electron-Acceptor: Hole-acceptor and electron-acceptorare relative terms for describing charge transfer between two materials.E.g., for two semiconductor materials wherein a first material has avalence band edge or highest occupied molecular orbital (HOMO) that ishigher than the corresponding valence band edge or HOMO for a secondmaterial, and wherein the first material has a conduction band edge orlowest unoccupied molecular orbital (LUMO) that is higher than thecorresponding conduction band edge or LUMO for the second material, thefirst material is a hole-acceptor with respect to the second materialand the second material is an electron-acceptor with respect to thefirst material. A particular band edge or molecular orbital is said tobe “higher” when it is closer the vacuum level.

Inorganic Materials: Materials which do not contain carbon as aprincipal element. The oxides and sulphides of carbon and the metalliccarbides are considered inorganic materials.

Nanostructured Network Layer: generally refers to a film of materialhaving features characterized by a width, or other characteristicdimension, on the order of several nanometers (10⁻⁹ m) across.Nanostructured network layers may be produced by several techniques,including:

(a) Intercalation and/or grafting of organic or polymeric moleculeswithin a mineral lamellar network comprised of clays, phosphates,phosphonates, etc. The lamellar compounds serve as a network host thatpreserves the pre-established structural order. Organic molecules arethen inserted or grafted into this pre-structured network (which iscomprised of mineral(s)).(b) Synthesis by electrocrystallisation of hybrid molecular assemblies.This synthesis technique drives the construction of highly organizedmineral networks with relatively long-range order that can be controlledand adjusted for electronic intermolecular transfer.(c) Impregnation of preformed inorganic gels. In an example of thistechnique, a silica xerogel can be formed by hydrolysis andpolycondensation of silicon alkoxides with organic monomers (e.g. withmonomers that are susceptible to polymerization within the porous gelstructure). Methylmethacrylate (MMA) is an example of a suitable organicmonomer and the inorganic-organic hybrid obtained after polymerizationof the MMA has optical and mechanical properties often superior to theindividual components.(d) Synthesis from heterofunctional metallic alkoxides metallic halidesor silsesquioxannes: Precursors of this kind have the formulaR_(x)M(OR′)_(n−x) or 3(R′O)Si—R″—Si(OR′)3, where R and R′ are eitherhydrogen (H), any organic functional group or a halide, R″ can be oxygenor an organic functional group, and M is a metal. Typically R and R′involve oxygen, e.g., —O—R and —O—R′. M may be any transition metal,e.g., titanium, zinc, zirconium, copper, lanthanum, niobium, strontium,or silicon, etc. The hydrolysis of alkoxy groups (OR′) followed by acondensation reaction will form the mineral network and the R groupswill imprint in the network the organic function.(e) Synthesis of hybrid networks through the connection of well-definedfunctional nanobuilding blocks. The pre-formatted species or buildingblocks could be in this case oxo-metallic clusters, nanoparticles,nano-rods, nano-tubes, nano-whiskers (CdS, CdSe, . . . ), metallic oroxides colloids, organic molecules or oligomers. These blocks arefunctionalized during or after their synthesis with complementaryspecies for tailoring the interface between organic and inorganicdomains.(f) Templated growth of inorganic or hybrid networks by using organicmolecules, macromolecules, proteins or fibers as structure directingagents. In general, molecules like amines, alkyl ammonium ions,amphiphilic molecules or surfactants can be used as templates to build astructured mineral network. Materials of the zeolites families are amongthe most intensively investigated systems. Molecular and supramolecularinteractions between template molecules (surfactants, amphiphilic blockcopolymers, organogelators, etc. . . . ) and the growing hybrid ormetal-oxo based network permit the construction of complex hybridhierarchical architectures.(g) Templated growth using nanoparticles, as structuring agents followedby removal of the nanoparticles, leaving behind a porous network. Thenanoparticles may be made, e.g., of latex, and removed, e.g., by heatingthe templated film to a sufficient temperature to “burn off” thenanoparticles.

Optoelectronic Device: A device that interacts with radiation andelectric current. Such a device could be a radiation-emitting device,e.g. a light-emitting diode (LED) or laser, or a radiation absorbingdevice, e.g. a photodetector/counter, photovoltaic cell (solar cell) orradiation-driven electrolysis cell.

Organic Solar Cell: A type of solar cell wherein an active photoelectriclayer is fabricated, either partly or entirely, using organic materialscomprising, e.g., polymers, oligomers, molecules, dyes, pigments(including mixtures) that are predominantly carbon based compounds.These materials may be insulating, conductive or semiconductive or mixesthereof.

Phase Separation: Two materials are said to be phase separated when theyform two distinct phases (analogous, e.g., to oil on water) as opposedto being thoroughly intermixed, e.g., in a solution or suspension.

Photovoltaic Device: A type of optoelectronic device that absorbsradiation and coverts energy from the radiation into electrical energy.

Radiation: Energy which may be selectively applied includingelectromagnetic energy having a wavelength between 10⁻¹⁴ and 10⁴ metersincluding, for example, gamma radiation, x-ray radiation, ultravioletradiation, visible light, infrared radiation, microwave radiation andradio waves.

Semiconductor: As used herein, semiconductor generally refers to amaterial characterized by an electronic bandgap typically between about0.5 eV and about 3.5 eV.

Surfactant Templation: In general, surfactant temptation is a particularsubcategory of templated growth. As used herein, surfactant temptationrefers an approach toward achieving pore size control of inorganic ororganic frameworks, e.g., by using surfactants or block copolymers astemplates to build a structured mineral network.

Solar Cell: A photovoltaic device that interacts with radiation (oftenin the form of sunlight) impinging on the device to produce electricpower/voltage/current.

Organic Materials: Compounds, which principally consist of carbon andhydrogen, with or without oxygen, nitrogen or other elements, exceptthose in which carbon does not play a critical role (e.g., carbonatesalts). Examples of organic materials include:

(a) Organic Dyes and pigments such as perylenes, phthalocyanines,merocyanines, terylenes and squaraines and their derivatives.

(b) Polymers: Materials consisting of large macromolecules composed ofmore than one repeating units. Polymers, composed of 2-8 repeating unitsare often referred to as oligomers. Examples of such repeating unitsinclude, e.g., dyes or pigments.

II. GENERAL OVERVIEW

Although the following detailed description contains many specificdetails for the purposes of illustration, anyone of ordinary skill inthe art will appreciate that many variations and alterations to thefollowing details are within the scope of the invention. Accordingly,the exemplary embodiments of the invention described below are set forthwithout any loss of generality to, and without imposing limitationsupon, the claimed invention.

Embodiments of the present invention implement a device layerarchitecture wherein two materials with complementary charge transfermaterials are configured such that (1) the presence of the two materialsregularly alternates on a nanometer scale and (2) an interfacial layerbetween the two materials enhances an efficiency of a device thatincorporates the architecture. By way of example, the interfacial layermay be configured to enhance efficiency in the form of one or more of(a) charge transfer between the two materials that exhibits differentrates for forward versus backward transport; (b) differential lightabsorption to extend a range of wavelengths that the active layer canabsorb; or (c) enhanced light absorption and/or charge injection. Thesethree enhancements are referred to below as enhancements (a), (b), and(c) respectively. In some embodiments, dopants may be incorporated intoone or more of the two materials on either side of the interfaciallayer, e.g., to promote charge transport.

FIG. 1 depicts a cross-sectional schematic diagram of an active layer100 according to an embodiment of the present invention. The activelayer 100 generally includes a nanostructured network layer 102, one ormore interfacial layers 103, and one or more network filling materials104, 106. It is desirable for the nanostructured network layer 102 andthe network-filling materials 104, 106 to have complementarycharge-transfer properties. The active layer 100 may include an optionalinterface layer 108 between the nanostructured network layer 102 and anunderlying electrode. The optional interface layer 108 may be made fromthe same material as the nanostructured network layer 102.

The nanostructured network layer 102 contains substantially uniformlydistributed, e.g., regularly spaced, structures roughly 1 nm to 100 nmin diameter and more preferably, about 10 nm to about 30 nm in diameter.In general, neighboring structures are spaced apart by between about 1nm and about 100 nm, measured, e.g., from nearest edge to nearest edge.More preferably, the structures are between about 10 nm apart and 30 nmapart, edge-to-edge. In many optoelectronic devices, e.g. photovoltaicdevices, it is desirable for the size and spacing of the structures tobe on the order of the exciton diffusion length in the material of thenanostructured network layer 102 and network filling materials 104, 106.A substantially uniform distribution of the structures can enhance theoverall conversion efficiency of the active layer 100. Thenanostructured network layer 102 is made from an inorganicelectron-accepting material, such as titania, tin oxide or another metaloxide. In the case of a complementary structure the nanostructurednetwork layer 102 may be made from an organic hole-accepting material.

The nanostructured network layer 102 may be made from an inorganiccompound (e.g., an oxide, nitride, oxynitride, etc.) based on a centralelement X. The central element X may be a transition metal, e.g., Ag,Au, Cd, Co, Cr, Cu, Fe, Ir, Mn, Mo, Nb, Ni, Sr, Ta, Ti, V, W, Y, Zn, Zr,etc. In a preferred embodiment, the central element X is titanium (Ti).In particular, nanostructured network layers made of semiconductingtitania (TiO₂) are of interest. Titania is an example of anelectron-accepting/transporting material. With a band gap of 3.2 eV,Titania (TiO₂) absorbs light from the near-ultraviolet region of thespectrum, and the material has relatively high charge mobility. ThusTitania has desirable electronic properties for effectivecharge-splitting in an active layer of an optoelectronic device.Furthermore, Titania is widely available and relatively inexpensive.Other suitable central elements X include Al, B, Ba, Pb, Se, Si, and Sn.

One or more network filling materials may be used to fill the spacesbetween the structures in the nanostructured network layer 102. In theexample shown in FIG. 1 the spaces are filled using first and secondnetwork filling materials 104, 106. The first network-filling material104 may be a hole-accepting, organic material. In the case of acomplementary structure, the first network-filling material 104 may bean electron-accepting inorganic material. Examples of suitable inorganicmaterials for the first network-filling material 104 include silicon(e.g., with suitable dopants), CdTe, oxides of transition metals, e.g.,CuO, ZnO, ZrO TiO₂ and the like.

Examples of suitable organic materials for the first network-fillingmaterial 104 include conjugated polymers such as poly(phenylene) andderivatives thereof, poly(phenylene vinylene) and derivatives thereof(e.g., poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene(MEH-PPV), poly(para-phenylene vinylene), (PPV)), poly(thiophene) andderivatives thereof (e.g., poly(3-octylthiophene-2,5,-diyl),regioregular, poly(3-octylthiophene-2,5,-diyl), regiorandom,Poly(3-hexylthiophene-2,5-diyl), regioregular,poly(3-hexylthiophene-2,5-diyl), regiorandom), poly(thienylenevinylene)and derivatives thereof, and poly(isothianaphthene) and derivativesthereof. Other suitable polymers include organometallic polymers,polymers containing perylene units, poly(squaraines) and theirderivatives. Other suitable organic network-filling materials includeorganic pigments or dyes, azo-dyes having azo chromofores (—N═N—)linking aromatic groups, phthalocyanines including metal-freephthalocyanine; (HPc), perylenes, naphthalocyanines, squaraines,merocyanines and their respective derivatives, poly(silanes),poly(germinates),2,9-Di(pent-3-yl)-anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10-tetrone,and2,9-Bis-(1-hexyl-hept-1-yl)-anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10-tetrone.

The second network-filling material 106 may be inorganic e.g., a metal,or organic e.g., a pigment dye or polymer. Examples of suitable organicmaterials include PEDOT (Baytron), polyaniline or polyacetylene dopedwith a dopant such as polystyrene sulfonic acid (PSS). In a particularembodiment, the second network filling material 106 ispoly-3,4-ethylenedioxythiophene-polystyrenesulfonic acid (PEDOT-PSS).

The interfacial layer 103 may be a single layer or a multi-layerstructure having two or more sub-layers. Appropriate configuration ofthe optional interfacial layer 103 can provide the active layer 100 withthe desired enhanced efficiency. For example, with respect toenhancement (a) above, the interfacial layer 103 can be configured suchthat charge-carriers traveling from the nanostructured network layer 102to the network-filling material 104 are transported at a different ratethan the same type of charge-carriers traveling from the network-fillingmaterial 104 to the nanostructured network layer 102.

An example of a material for an interfacial layer 103 is carboxylic acid(COOH) functionalized buckminsterfullerene (C₆₀), also known asC₆₀-acid. The structure of C₆₀-acid is depicted schematically in FIG.2A. The carboxylic acid functionalization provides layers of C₆₀ withinteresting electronic properties. Specifically, electron transfer outof a C₆₀-acid layer occurs at a lower rate than electron transfer intothe C₆₀-acid layer. In particular, electron transfer into a layer ofC₆₀-acid occurs with a characteristic time constant on the order of40-50 femtoseconds while electron transfer out of the same layer occurswith a time constant of order about one millisecond. Thus electrons arefar more likely to transfer into the carboxylic acid functionalized C₆₀layer than out of it. Consequently, a layer of carboxylic acidfunctionalized C₆₀ can act as a “one-way gate” for electron transfer.

To make use of the electronic properties of C₆₀, it is important to beable to attach the molecule to a surface so that is can be covalentlybonded to and thus function as an integrated component of that surface.To do so, C₆₀ can be functionalized with a COOH moiety. Alternatively,C₆₀ or another fullerene could be functionalized with molecules otherthan COOH. For example one could make an ester, amide, amine, acid, andso forth to have any of these (or other) chemical linkage groupsattached to the fullerene itself. In addition, other functionalizedfullerenes may be used in the interfacial layer 103. Such functionalizedfullerenes could be mono adducts, or dual adducts, and could be in anyof several forms, including C₆₀, C₇₀, C₇₆, and C₈₄. For each form, manytypes of functionalization are possible, e.g., acid-, ester-, amide-, oramine-functionalization, any of which could be useful.

FIG. 2B shows an example of an alternative functionalized fullerenestructure. In FIG. 2B, R can be any organic functional group. Onepossible compound within the scope of the structure of FIG. 1B is[6,6]-Phenyl C₆₁-butyric acid methyl ester [11] (PCBM). The enhancedsolubility of PCBM compared to C₆₀ allows a high fullerene-conjugatedpolymer ratio. The structures shown in FIG. 2A and FIG. 2B are but twoparticular examples of a general functionalized fullerene structure.Many other possible functionalized structures are suitable for use withembodiments of the present invention. Thus, FIGS. 2A and 2B representtwo of several ways to functionalize a fullerene and are by far not theonly means of doing so. Furthermore, as an alternative to functionalizedfullerenes, the interfacial layer 103 may alternatively usefunctionalized carbon nanotubes.

With respect to enhancement (b), the interfacial layer 103 can beconfigured to differentially absorb light, e.g., by providing the activelayer 100 with two different phase-separated light-absorbing layers. Forexample, the interfacial layer 103 may be a photoactive material thatabsorbs light over an absorption band, i.e., a range of wavelengths,that partially overlaps an absorption band for the first network-fillingmaterial 104. A convolution of the two absorption bands can thus providethe active layer 100 as a whole with a broader absorption band thaneither the interfacial layer 103 or first network filling material 104by itself. The interfacial layer 103 may be made of two or moresub-layers, each having a different absorption band, to provide an evenbroader absorption band for the active layer 100. The interfacial layer103 may be made from materials in the same category (e.g., organic orinorganic) as the network-first filling material 104 but is a differentmaterial within that category. Examples of suitable organic andinorganic photoactive materials for the interfacial layer 103 includethose listed above with respect to the first network-filling material104 and their equivalents.

With respect to enhancement (c) above, the interfacial layer 103 may beconfigured to enhance light absorption and/or charge injection, e.g.with pigments or dyes. In the case of a PV device, at least one of thenanostructured network layer 102, and network-filling materials 104, 106is a light absorbing material and at least one of these is an electrontransporting material. The dye or pigment in the interfacial layer canenhance light absorption in the light absorbing material and/or chargeinjection from the light absorbing material to the electron absorbingmaterial. Examples of suitable dyes include perylene, ru-polypyridyl,porphoryins, azo-dyes having azo chromofores (—N═N—) linking aromaticgroups, phthalocyanines including metal-free phthalocyanine; (HPc),perylenes, naphthalocyanines, squaraines, merocyanines and theirrespective derivatives, poly(silanes), poly(germinates),2,9-Di(pent-3-yl)-anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10-tetrone,and2,9-Bis-(1-hexyl-hept-1-yl)-anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-1,3,8,10-tetrone.Several photosensitizer dyes of the Ru-polypyridine family can also beused: e.g., [(CN)(bpy)₂Ru—CN—Ru(dcbpy)₂-NCRu(bpy)₂],[Ru(4,4-bis(carboxy)-bpy)₂(NCS)₂] and [Ru(2,2′,2″-(COOH)₃-terpy)(NCS)₃].The interfacial layer 103 may include two or more sub-layers, each ofwhich may have a different pigment or dye. Furthermore, two or moredifferent dyes may be combined within the same sub-layer.

In a particular embodiment suitable for photovoltaic applications, thenanostructured network layer 102 may be made of an electron-acceptinginorganic material, such as titania (TiO₂), the interfacial layer 103may be a layer of carboxylic acid functionalized buckminster fullerene(C₆₀-acid), the first network filling material 104 may be ahole-accepting polymer such as MEH-PPV or P3HT and the second networkfilling material 106 may be a conducting polymer such as PEDOT-PSS. Insuch an active layer electrons that have been split away from holes movethrough the hole-accepting polymer into the interfacial layer 103 theninto the titania much faster than they move from the titania back intothe interfacial layer 103 then into the semiconducting polymer. Aftercharge splitting, the C₆₀-acid or other interfacial layer material wouldkeep electrons on one side and holes on the other, so they cannotrecombine before the electrons are pulled out of the device to generateelectricity.

There are several alternative embodiments within the scope of thepresent invention. For example, the first network-filling material 104may be a hole-accepting inorganic material, such as copper oxide. Ifsuch were the case in a hybrid organic-inorganic active layer, thenanostructured network layer 102 would be an electron-acceptingmaterial.

Furthermore, in the case of a complementary hybrid organic-inorganicstructure, the nanostructured network layer 102 may be a hole-acceptingorganic material and the first network filling material 104 may be anelectron-accepting inorganic material. In an example of a complementarystructure, a porous silica-based template mold may be filled with aninorganic electron-accepting material. The template mold may bedestroyed and washed away leaving behind a nanostructured network layer102, e.g., in the form of “columns” of the inorganic material. Theinterfacial layer 103 may be disposed on the columns and spaces betweenthe columns may then be filled with organic hole-acceptingnetwork-filling material(s) 104, 106.

In some embodiments, the interfacial layer 103 may use some mixture ofdyes, pigments, photoactive materials, fullerenes and/or carbonnanotubes, either in the same layer, or in different sub-layers. Thus,the interfacial layer 103 may implement combinations of two or more ofthe enhancements (a), (b) and (c). For example, two or more enhancementsmay be combined within the same sub-layer or with each in a differentsub-layer or with two or more different enhancements combined in each oftwo or more different sub-layers. There are a number of differentpossible variations on these combinations that are within the scope ofembodiments of the present invention.

In some embodiments, the nanostructured network layer 102 and/orinterface layer 108 may optionally include one or more dopants 105 todifferentially configure the charge transfer properties of the activelayer 100. For example, an X-based oxide nanostructured network layermight be doped with fullerenes (e.g., C₆₀), metals, or other materialsthat affect charge transport and/or light absorption and/or chargeinjection. If fullerenes are used as the dopants 105 to enhance chargetransport, it is often desirable to dope the fullerenes that arenormally semiconducting with atoms that make them conducting or“metallic”. Alternatively, the nanostructured network layer 102 may bedoped with lithium, indium, and rare earth metals (such as europium).Although, for the sake of simplicity, only the nanostructured networklayer 102 is shown as being doped it is possible instead to dope one ormore of the network filling materials 104, 106 in ways that provide thedesired configuration of charge transport properties. Furthermore, boththe nanostructured network layer 102 and the network filling materials104, 106 may be doped. In addition, although the active layer 100 isdepicted having both an interface layer 103 and dopants 105, it ispossible to use one without the other.

FIG. 3 depicts a simplified and somewhat idealized diagram of adesirable morphology for a nanostructured network layer 300 that may beused in the active layer 100 of FIG. 1. The nanostructured network layer300 has structures 302 with spaces in the form of pores 301 betweenneighboring structures 302. The pores may run along x, y and zdirections and intersect with each other as shown in the inset in FIG.3. The pores 301 may be characterized by a diameter d. Thenanostructured network layer 300 may be characterized by a spacing Dbetween neighboring pores 301, measured e.g., from edge-to-edge. Thepore diameter d and pore spacing D are substantially uniform across thenanostructured network layer 300. The pores 301 are interconnected witheach other in a way that provides continuous paths between oppositesurfaces of the nanostructured network layer 300. The paths through thepores 301 provides access to the pores from a layer overlying or a layerunderlying the nanostructured network layer 300. When the pores 301 arefilled with a suitable network-filling material, charges can migratethrough the network-filling material from the overlying layer to theunderlying layer and/or vice versa.

It is often desirable for the pores 301 to have a high aspect ratio. Anaspect ratio of 100 (e.g., 10 nm diameter pores 1000 nm deep) issuitable for many optoelectronic device applications.

The nanostructured network layer 300 may serve as a sacrificial templatefor making a nanostructured grid network. The structures 302 may beremoved, e.g., by etching, after the pores 301 are filled with the porefilling material leaving behind a nanostructured grid network havingstructures (e.g., columns) made of the network-filling material. Thecolumns can be roughly characterized as having diameter d andneighboring structures are separated by a distance of approximately Dmeasured edge-to-edge. Empty spaces between the columns can then befilled with a network filling material having complementary chargetransfer properties with respect to the pore filling material that formsthe structures.

III. OPTOELECTRONIC DEVICE ARCHITECTURE

FIG. 4 depicts an example of a device structure for an optoelectronicdevice 400 according to an embodiment of the present invention. Theoptoelectronic device 400 generally includes an active layer 401disposed between a transparent conducting electrode (TCE) 402 a baseelectrode 404. The device 400 may be modularized by well-knownencapsulation in order to improve weather resistance and mechanicalstrength e.g., with an optional substrate and/or encapsulant layers 406,408.

The active layer 401 includes a nanostructured network layer 403 and oneor more network filling materials e.g., semiconducting and conductingnetwork-filling materials 405, 407 respectively as described above withrespect to FIG. 1. The nanostructured network layer 405 may have astructure of the type described above with respect to FIG. 3. Thenanostructured network layer may include dopants 409, (e.g.,functionalized fullerenes, metals, etc.) as described above. Aninterfacial layer 411 (e.g., functionalized fullerene, etc.) may bedisposed between the nanostructured network layer 403 and the networkfilling materials 405, 407, as described above with respect to FIG. 1.An interface layer 413 may be disposed between the base electrode 404and the nanostructured network layer 405.

The TCE 402 may be a layer of transparent conducting oxide (TCO) such asindium tin oxide (ITO). The TCE 402 may optionally include (either withor without a TCO) some combination of a transparent conducting polymer,a thin metal layer or an array of spaced apart wires, e.g., in the formof a mesh, grid or parallel wires.

The base electrode 404, may be in the form of a commercially availablesheet material such as such as C-, Au-, Ag-, Al-, or Cu-coated SteelFoil or metal/alloy-coated plastic foils, including metal or metalizedplastic substrates/foils that are planarized to reduce surfaceroughness. The base electrode 404 may optionally be a TCE.

The optional encapsulants 406, 408 protect the optoelectronic device 400from the surrounding environment. The encapsulants 406, 408 may alsoabsorb UV-light to protect organic materials disposed between theencapsulants 406, 408. Examples of suitable encapsulant materialsinclude one or more layers of glass or polymers, such as polyethyleneterephthalate (PET) and/or Mylar®. Mylar is a registered trademark of E.I. du Pont de Nemours and Company of Wilmington, Del. Either encapsulantlayers 406, 408 may include EVA (ethylene vinyl acetate), which hasfavorable adhesive, weather resistance, and buffer effect properties.

In order to further improve moisture resistance and scratch resistance,a fluorine resin may be laminated to the encapsulant layers 406, 408 asa surface protecting layer. For example, tetra-fluoro ethylene copolymer(TFE, Du Pont TEFLON), copolymer of tetra-fluoroethylene and ethylene(ETFE, Du Pont TEFZEL), polyvinyl fluoride (Du Pont TEDLAR),polychlorofluoroethylene (CTFEC, Daikin Industries Neoflon) may be used.Weather resistance can also be improved by adding a well-known UVabsorber. In addition to glass, other inorganic materials, such asceramics and metal foils may also be used for the encapsulants 406, 408.The encapsulants 406, 408 may also include nitrides, oxides, oxynitridesor other inorganic materials that protect against exposure to water orair. In particular, the encapsulant may be a multi-layer stack or a foilcomprising a multi-layer stack of organic materials with inorganicdielectrics.

IV. ACTIVE LAYER FABRICATION

An active layer for an optoelectronic device of the type described abovemay be fabricated according to a method according to an embodiment ofthe present invention. FIG. 5 depicts of flow diagram illustrating themethod. The method is best understood by referring to FIG. 4 and FIG. 5.The method begins at 502 by forming the nanostructured network layer403. Subsequently, at 504, spaces in the nanostructured network layerare filled with one or more network-filling materials 405, 407. At 506an interfacial layer is disposed between the nanostructured networklayer 403 and the network filling materials 405, 407. At 508 theinterfacial layer 403 is configured to enhance an efficiency of theresulting active layer 401 or device 400. For the sake of simplicity, inFIG. 5 the configuring step 506 is shown after steps 502, 504 and step508 is shown after step 506.

As a practical matter the interfacial layer disposition step 506 canoccur between the nanostructured layer formation step 502 and thenetwork-filling step 504. The acts that constitute the configuring step508 may occur before, during, after and/or in conjunction with step 502,504 or 506.

With respect to step 502, examples of techniques for forming thenanostructured network layer 403 include, but are not limited to: (a)Intercalation and/or grafting of organic or polymeric molecules within amineral lamellar network; (b) synthesis by electrocrystallisation ofhybrid molecular assemblies; (c) impregnation of preformed inorganicgels; (d) synthesis from heterofunctional metallic alkoxides metallichalides or silsesquioxannes; (e) synthesis of hybrid networks throughthe connection of well-defined functional nanobuilding blocks; (f)templated growth of inorganic or hybrid networks by using organicmolecules, macromolecules, proteins or fibers as structure directingagents; and (g) templated growth using nanoparticles as structuringagents followed by removal of the nanoparticles.

In a particular embodiment nanostructured network layers of the typedescribed with respect to FIG. 1 and FIG. 3 may be formed by surfactanttemplation using a precursor sol. Examples of surfactant-templationtechniques for producing porous films are described, e.g., by Brinker,et al in U.S. Pat. No. 6,270,846, the disclosures of which areincorporated herein by reference. The precursor sol generally includesone or more alkoxides with a central element X, one or more surfactants,one or more condensation inhibitors, water, and a solvent. The solventcan be a polar organic solvent or any other solvent that solubilizes theother reactants. Examples of suitable solvents include alcohols, (e.g.,methanol, ethanol, propanol, butanol), tetrahydrofuran, and formamide ormixtures thereof. For TiO₂-based porous surfactant templated filmsexamples of suitable alkoxides include titanium ethoxide or titaniumisopropoxide. For SiO₂-based surfactant templated films examples ofsuitable alkoxides include polysiloxanes such as tetraethylorthosilicate(TEOS). As part of the configuring step 506 dopants may optionally beadded to the precursor sol. Dopants such as fullerenes, (doped orundoped) metals, etc. may be added to the sol e.g., from a stocksolution. To dope with a metal, an alkoxide of the metal can be mixedwith the alkoxides(s) of central element X (for example titaniumisopropoxide) in the sol gel precursor stock.

Examples of suitable surfactants includeHO(CH₂CH₂CO)_(n)(CH₂CHCH₃O)_(m)(CH₂CH₂O)_(n)H, where the subscripts mand n are integers. A particular surfactant of this type is the blockcopolymerpoly(ethyleneoxide)-b-poly(propyleneoxide)-b-poly(ethyleneoxide) (n=20,m=70, n=20), sometimes known commercially as Pluronic P123. Pluronic isa registered trademark of BASF Corporation of Ludwigshafen, Germany.Other suitable surfactants include hexadecyl trimethylammonium bromide(CTAB), polyoxyalkylene ether (e.g. Pluronic F127), andpoly(oxyethylene) cetyl ether (e.g., Brij56 or Brij58) Brij is aregistered trademark of Atlas Chemicals of Wilmington Del. Brij 56 isalso known as polyoxyethylene 10 cetyl ether. Brij 58 has severalsynonyms, including poly(oxyethylene) cetyl ether, poly(oxyethylene)palmityl ether, polyethylene oxide hexadecyl ether, and polyethyleneglycol cetyl ether.

Examples of suitable condensation inhibitors include acids such ashydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃),etc., bases such as sodium hydroxide (NaOH), triethylamine, etc., andchelating agents, including acetyl acetone, alcohol amines, peroxides,etc.

Generally speaking, the molar ratios of the surfactant, condensationinhibitor, ethanol and water may be in the following ranges with respectto the central element X, where X refers to the central element orinorganic network atom in the alkoxide:

[Surfactant]/[X]: a molar ratio ranging from about 1×10⁻⁷ to about 0.1

[Solvent]/[X]: a molar ratio ranging from about 3 to about 50

[Condensation Inhibitor]/[X]: a molar ranging ratio from about 1×10⁻⁵ toabout 5

[water]/[X]: a molar ratio ranging from about 0 to about 20.

The sol may be filtered and a thin film prepared from this solution maybe disposed on a substrate by spin-coating, web-coating, dip-coating,spray-coating, ink-jet printing, doctor blade coating, spray coating,printing such as screen-printing, ink-jet printing, flexographicprinting, gravure printing, micro-gravure printing, and the like. Whenmaking a device of the type shown in FIG. 4, the substrate may be thebase electrode 404. In such a case, the precursor sol may be disposeddirectly on the surface of the base electrode 404, or the surface of anintervening layer such as the interface layer 413. The solvent isevaporated from the precursor sol to form a surfactant-templated porousfilm.

The surfactant-templated porous film may be covalently crosslinked topermanently fix its structure. The crosslinking may be implemented,e.g., by heating the surfactant templated film. During this step, thesurfactant templates can be also be selectively removed, e.g., throughexposure to heat. By way of example, heating the as-coated film tobetween about 170° C. and about 400° C. is typically sufficient tocovalently crosslink the surfactant-templated porous film and/ordecompose the surfactant molecules while remaining within the thermalstability range of the underlying substrate.

Furthermore, either as an alternative to heating, or in conjunction withheating, the surfactant template may be exposed to energetic radiation,such as ultraviolet (UV) radiation, to facilitate crosslinking of thegrid to form a mesoporous grid and to destroy the structure of thesurfactant and make it easier to wash out.

In some embodiments the crosslinked surfactant-templated porous filmserves as the nanostructured network layer. For example, where X istitanium, the crosslinked surfactant-templated porous film can provide aTiO₂ nanostructured network layer with a structure like that shown inFIG. 3. Alternatively X may be silicon, in which case a structure likethat shown in FIG. 3 made of SiO₂ can serve as a porous template. Thepores in the template may be filled with a suitable inorganicpore-filling material, e.g., by electrodeposition. The SiO₂ template maythen be removed, e.g., by chemical etching in a solution of sodiumhydroxide (NaOH), potassium hydroxide (KOH), or hydrofluoric acid (HF)followed by suitable washing of any SiO₂ debris. The removal of theporous template leaves behind structures made from the pore fillingmaterial with essentially the same size and shape as the pores. Thestructures are separated by spaces left behind by the removal of theporous template film.

With respect to 504, the network-filling materials 405, 407 may beprovided in the form of process solutions containing a precursormaterials and solvents. As part of this step, the process solution forforming the semiconducting network filling material 405 may includedopants that provide the network-filling materials 405, 407 withdesirable charge transfer and/or light absorption properties. Theprocess solution may be applied to the nanostructured network layer 403by any suitable technique, e.g., web-coating, doctor blade coating,spray coating, spin coating, or a printing technique such as printingsuch as screen-printing, ink-jet printing, flexographic printing,gravure printing, micro-gravure printing, and the like. Heat may beapplied to the nanostructured network layer and network-filling materialduring this step, e.g., to evaporate solvents and set thenetwork-filling material and/or to assist material infiltration, e.g.,through capillary action and/or osmotic force.

With respect to the interfacial layer disposition step 506, theinterfacial layer 411 may be disposed between the nanostructured networklayer 403 and the network filling materials 405, 407 by coating thenanostructured network layer 403 before filling the spaces with thefirst network filling material 405. The interfacial layer 411 coats asurface of the nanostructured network layer 403 including at least aportion of the walls of one or more of the structures. For example, astock solution or process solution for forming the desired interfaciallayer 411 may be disposed on the surfaces of the structures in thenanostructured network layer 403, e.g., by spin-coating, web-coating,dip-coating, spray-coating, ink-jet printing, doctor blade coating,spray coating, printing such as screen-printing, ink-jet printing,flexographic printing, gravure printing, micro-gravure printing, and thelike. Solvents can then be evaporated from the stock or process solutionleaving behind the desired interfacial layer 411. In embodimentsinvolving an interfacial layer 411 with multiple sub-layers, eachsub-layer may be laid down in sequence using different stock solutionsor process solutions. The solvent may be evaporated from one sub-layerbefore setting down the solution for the next sub-layer.

With respect to enhancement (a) the configuration step 508 may involveconfiguring the interfacial layer such that charge-carriers travelingfrom the nanostructured network layer 403 to the network-fillingmaterial(s) 405/407 are transported at a different rate than the sametype of charge-carriers traveling the other way round. As describedabove, the interfacial layer 411 may include a functionalized fullerene,carbon nanotube, dye or other suitable material. By way of example, afullerene (e.g., C₆₀) can be functionalized before coating in anindependent, parallel reaction, then stored in a stock solution untilneeded for disposition on surfaces of the nanostructured network layer403.

One approach, among others, to making a functionalized fullerene stocksolution is to start with1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (C₆₀-acid)prepared along the following lines. Reaction of C₆₀ and(ethoxycarbonyl)methyl diazoacetate yields an isomer mixture, which isequilibrated to methanofullerene ester after heating in toluene, afterwhich the ester is hydrolyzed to C₆₀-acid by treatment with borontribromide in benzene. As stated above, C₆₀ (or other fullerenes) couldalso be functionalized with molecules other than COOH—e.g. one couldmake an ester, amide, amine, acid, and so forth to have any of these (orother) chemical linkage groups attached to the fullerene itself. Forexample, to make a reactive ester of the C₆₀-acid one can use commonreagents such, as N-Hydroxysuccinimide (NHS) or dicyclohexylcarbodiimide(DCI).

In the case of a nanostructured network layer 403 made of a metal oxidesuch as TiO₂ it is also important to “functionalize” the oxide surfaceto permit some —OH groups to form, which can then react with theappropriate functional group such as a carboxylic acid moiety on the C₆₀molecule. To functionalize the titania surface, one typically exposesthe surface first to a base, e.g., NaOH and the like, and then to anacid, e.g., HCl and the like. Exposing the surface to a base andconverting the bound oxygen into a liberated OH—e.g. by hydrolyzing abond can increase the local oxygen content on the surface.Alternatively, one could treat the surface with an agent that wouldliberate some of the —OH groups on the titania surface, e.g. bygenerating metal-OH groups on the surface of the metal oxide, making anactive ester of the C₆₀—COOH, and attaching it to the metal-OH region ofthe metal oxide.

With respect to enhancement (b), the configuration step 508 may involveproviding the interfacial layer 411 with differential light absorptionthrough appropriate choice of the photoactive materials that will formthe first network filling material 405 and the interfacial layer 411. Insuch a case, the interfacial layer 411 can be prepared from a stocksolution similar to the process solution used to form the firstinterfacial layer 405.

With respect to enhancement (c), the configuration step may involveproviding the interfacial layer 411 with enhanced light absorption,e.g., through appropriate choice of the pigment or dye in theinterfacial layer 411. In such a case, the interfacial layer 411 can beprepared from a stock solution similar to the process solution used toform the first interfacial layer 405.

Once the spaces in the nanostructured network layer 403 have been filledwith the interfacial layer 411 and the first network-filling materials405, the rest of the device 400 may be fabricated in a relativelystraightforward fashion. For example, an additional process solution maybe applied over the first network-filling material 405 to provide thesecond pore-filling material 407, which can act as an interface betweenthe first pore-filling material 405 and the TCE 402. At 510 the TCE 402can then be attached to or deposited on the surface of the active layer401 (e.g., the exposed surface of the second pore-filling material 407).The TCE 402, active layer 401 and base electrode 404 can then belaminated between the encapsulants 406, 408 at 512.

VI. CONCLUSION

While the above is a complete description of the preferred embodiment ofthe present invention, it is possible to use various alternatives,modifications and equivalents. It is to be understood that the abovedescription is intended to be illustrative and not restrictive. Manyembodiments and variations of the invention will become apparent tothose of skill in the art upon review of this disclosure. Merely by wayof example a wide variety of materials, precursors and reactionconditions may be utilized, as well as a different ordering of certainprocessing steps. The scope of the invention should, therefore, bedetermined not with reference to the above description, but insteadshould be determined with reference to the appended claims along withthe full scope of equivalents to which such claims are entitled.

1. An optoelectronic apparatus, comprising: an active layer including: ananostructured network layer having a network of regularly spacedstructures with spaces between neighboring structures, wherein thestructures are interconnected and wherein interconnections betweenstructures comprise of a material that is the same as a material used toform the structures; one or more network-filling materials disposed inthe spaces, wherein at least one network-filling material hascomplementary charge transfer properties with respect to the material ofthe nanostructured network layer; an interfacial layer disposed betweenthe nanostructured network layer and network-filling material, whereinthe interfacial layer is configured to enhance an efficiency of theapparatus; wherein the interfacial layer includes at least one of thefollowing: an acid-, ester-, amide-, amine-, or other-functionalizedfullerene, or functionalized carbon nanotubes.
 2. The apparatus of claim1 wherein the interfacial layer is configured such that charge-carrierstraveling from the nanostructured network layer to the network-fillingmaterial are transported at a different rate than the same type ofcharge-carriers traveling from the network-filling material to thenanostructured network layer.
 3. The apparatus of claim 2 wherein theinterfacial layer includes functionalized C₆₀, PCBM, C₆₀, C₇₀, C₇₆, C₈₄or other functionalized fullerenes in mono-adduct or dual-adduct mode.4. The apparatus of claim 1 wherein the interfacial layer is configuredto differentially absorb light to extend a range of wavelengths that theactive layer can absorb.
 5. The apparatus of claim 4 wherein theinterfacial layer includes a photoactive material that isphase-separated from a photoactive network filling material.
 6. Theapparatus of claim 5 wherein the photoactive material in the interfaciallayer is characterized by a different absorption band than thephotoactive network-filling material.
 7. The apparatus of claim 1wherein the interfacial layer is configured to enhance absorption oflight.
 8. The apparatus of claim 7 wherein the interfacial layerincludes one or more dyes or pigments.
 9. The apparatus of claim 7wherein the interfacial layer is configured to enhance charge injectionfrom a light absorbing material to an electron transporting material inthe active layer.
 10. The apparatus of claim 1 wherein one or more ofthe nanostructured network layer and the network filling materialincludes one or more dopants.
 11. The apparatus of claim 10 wherein theone or more dopants include one or more fullerenes, one or more metals,one or more dyes pigments or other photoactive materials.
 12. Theapparatus of claim 1 wherein the interfacial layer includes two or moresub-layers.
 13. The apparatus of claim 1 wherein the regularly spacedstructures are between about 1 nm and about 100 nm in diameter.
 14. Theapparatus of claim 13, wherein the regularly spaced structures arespaced apart by between about 1 nm and about 100 nm measured edge toedge.
 15. The apparatus of claim 1 further comprising: a base electrode;and a transparent conducting electrode; wherein the active layer isdisposed between the base electrode and the transparent conductingelectrode.
 16. The apparatus of claim 1 wherein the structures areregularly arrayed in at least 2 dimensions.
 17. The apparatus of claim 1wherein the interfacial layer comprises of a multi-layer structurehaving two or more sub-layers.
 18. The apparatus of claim 1 wherein thematerial comprises of an electron accepting material.
 19. Anoptoelectronic apparatus, comprising: an active layer including: ananostructured network layer having a network of regularly spacedstructures with spaces between neighboring structures; one or morenetwork-filling materials disposed in the spaces, wherein at least onenetwork-filling material has complementary charge transfer propertieswith respect to the material of the nanostructured network layer; aninterfacial layer disposed between the nanostructured network layer andnetwork-filling material, wherein the interfacial layer is configured toenhance an efficiency of the apparatus; wherein the interfacial layerhas a material property such that charge-carriers traveling from thenanostructured network layer to the network-filling material aretransported at a different rate than the same type of charge-carrierstraveling from the network-filling material to the nanostructurednetwork layer; wherein the interfacial layer includes at least one ofthe following: an acid-, ester-, amide-, amine-, or other-functionalizedfullerene, or functionalized carbon nanotubes.
 20. The apparatus ofclaim 19 wherein the interfacial layer includes functionalized C₆₀,PCBM, C₆₀, C₇₀, C₇₆, C₈₄ or other functionalized fullerenes inmono-adduct or dual-adduct mode.
 21. An optoelectronic apparatus,comprising: an active layer including: a nanostructured network layerhaving a network of regularly spaced structures with spaces betweenneighboring structures, wherein neighboring structures are shaped tointerconnect to each other in the network layer; one or more lightabsorbing, photoactive network-filling materials disposed in the spaces,wherein at least one network-filling material has complementary chargetransfer properties with respect to the material of the nanostructurednetwork layer; an interfacial layer disposed between the nanostructurednetwork layer and network-filling material, wherein the interfaciallayer is configured to enhance an efficiency of the apparatus; whereinthe interfacial layer includes at least one of the following: an acid-,ester-, amide-, amine-, or other-functionalized fullerene, orfunctionalized carbon nanotubes.
 22. The apparatus of claim 21 whereinthe interfacial layer is configured to differentially absorb light toextend a range of wavelengths that the active layer can absorb.
 23. Theapparatus of claim 21 wherein the interfacial layer includes aphotoactive material that is phase-separated from a photoactive networkfilling material.
 24. The apparatus of claim 23 wherein photoactivematerial in the interfacial layer is characterized by a differentabsorption band than the photoactive network-filling material.
 25. Theapparatus of claim 21 wherein the interfacial layer is configured toenhance absorption of light.
 26. The apparatus of claim 25 wherein theinterfacial layer includes one or more dyes or pigments.
 27. Theapparatus of claim 25 wherein the interfacial layer is configured toenhance charge injection from the light absorbing network fillingmaterial to an electron transporting material in the active layer. 28.The apparatus of claim 21 wherein one or more of the nanostructurednetwork layer and the network filling material includes one or moredopants.
 29. The apparatus of claim 28 wherein the one or more dopantsinclude one or more fullerenes, one or more metals, one or more dyespigments or other photoactive materials.
 30. The apparatus of claim 21wherein the interfacial layer comprises of a multi-layer structurehaving two or more sub-layers.
 31. The apparatus of claim 21 wherein thematerial comprises of an electron accepting material.
 32. Anoptoelectronic apparatus, comprising: an active layer including: ananostructured network layer having a network of regularly spacedstructures with spaces between neighboring structures; one or morenetwork-filling materials disposed in the spaces, wherein at least onenetwork-filling material has complementary charge transfer propertieswith respect to the material of the nanostructured network layer; aninterfacial layer disposed between the nanostructured network layer andnetwork-filling material, wherein the interfacial layer is configured toenhance an efficiency of the apparatus; wherein the interfacial layer isconfigured such that charge-carriers traveling from the nanostructurednetwork layer to the network-filling material are transported at adifferent rate than the same type of charge-carriers traveling from thenetwork-filling material to the nanostructured network layer; whereinthe interfacial layer includes at least one of the following:functionalized C₆₀, PCBM, C₆₀, C₇₀, C₇₆, C₈₄, other functionalizedfullerenes in mono-adduct or dual-adduct mode, acid-, ester-, amide-,amine-, or other-functionalized fullerene, or functionalized carbonnanotubes.